The long-term objectives of this proposal are to understand the neurobiological basis of complex cognitive, perceptual and motor processes from the standpoint of neurophysiological and neuroanatomical specializations of the left and right cerebral hemispheres. One aim of the proposed studies is to evaluate the effect of lateralization on the homolog to Broca's area, referred to as the inferior frontal gyrus, on the acquisition of oro-facial motor control. Specifically, chimpanzees that are left or right hemisphere dominant for the inferior frontal gyrus will be trained to produce a novel sound referred to as the raspberry (RASP). If the left inferior frontal gyrus is selectively involved in oro-facial motor learning, then left dominant chimpanzees should criterion on the oro-facial motor learning task significantly faster than the right hemisphere dominant individuals. A second aim is to evaluate the neural correlates of oro-facial motor control. Chimpanzees will be PET imaged when producing intentional referential vocal signals, referred to as the RASP as well as when making non-communicative oro-facial movements in the form of lip pouts. Of specific interest is identification of brain areas functionally used during the production of the RASP when controlling for basic motor movements of the mouth. The overall studies will contribute to our understanding of factors that influence individual and species differences in the expression of hemispheric specialization. PUBLIC HEALTH RELEVANCE: A variety of neurodevelopmental and psychological disorders are linked to variability in hemispheric specialization of the brain, particularly as it relates to higher order cognition and language. Therefore understanding the role of different factors on the development of hemispheric specialization is important for understanding how the brain develops and what the consequences are for disruption in these developmental processes. The proposed studies will provide important data on plasticity and the role of specific motor experiences on the development of hemispheric specialization.